More countersink questions

[imagineer]

The last item on my to-do list for the weekend was to drill & install roll pins in the anvil plates for the HF 20T hydraulic press. To accommodate stacking the plates, I counterbored the drilled holes to allow clearance for the extending roll pins.

Before inserting the pins, I opted to countersink the drilled holes and . . . it occurred to me that I really don’t know of any guidelines or standard practices for the selection and use of countersinks.

In my tool cache, I now have an ample collection of countersinks, zero flute, 1 flute, multiple flutes, diameters from ¼” to over 1”, 82* & 90*, carbide and HSS.

Asking the forum members:

What criteria governs which type of countersink to use, and at what rpm?

Are certain types of countersinks not good for use on steel?

Should cutting oil be used?

What would the reasons be for choosing a multi-flute over a 1-flute countersink?

Can/should a 1 flute countersink be used with a hand drill?

 

[projectnut]

The last item on my to-do list for the weekend was to drill & install roll pins in the anvil plates for the HF 20T hydraulic press. To accommodate stacking the plates, I counterbored the drilled holes to allow clearance for the extending roll pins.

Before inserting the pins, I opted to countersink the drilled holes and . . . it occurred to me that I really don’t know of any guidelines or standard practices for the selection and use of countersinks.

In my tool cache, I now have an ample collection of countersinks, zero flute, 1 flute, multiple flutes, diameters from ¼” to over 1”, 82* & 90*, carbide and HSS.

Asking the forum members:

What criteria governs which type of countersink to use, and at what rpm?

Are certain types of countersinks not good for use on steel?

Should cutting oil be used?

What would the reasons be for choosing a multi-flute over a 1-flute countersink?

Can/should a 1 flute countersink be used with a hand drill?

In my experience the best all-around countersinks are the HSS single flute style. Over the years I've used single flute, multi flute, and zero flute. All have been used on a variety of materials from wood to plastic. As far as metals I most commonly use 6061 aluminum, 304 (A2), and 316 stainless as well as 1014 carbon steel and various other steel alloys. All countersink styles seem to work well in rigid machines like either a mill or drill press. The best for hand drills are either the single or zero flute style. Multiflute styles have a tendency to chatter when used in a hand drill. All should be used with lubricant and at low speeds. On steel alloys I use heavy cutting oil. On aluminum I use WD40 with speeds generally in the 200 to 400 rpm range.

One advantage of single flute countersinks is that they are easy to sharpen on a surface grinder using fixture relative to the other styles. In addition, in a pinch you can also easily change the cutting angle.

Although I do have some carbide countersinks, they are generally only used on various grades of tool steels. They have a tendency to chip if not used in a rigid machine and are more difficult to resharpen.

On Edit: I forgot to say my favorite brands are MA Ford and KEO

 

[snoopdog]

I second what project nut said, single flute hss for 90%, multi flute will chatter every time with a hand drill, in my experience.

 

[GeneT45]

I like zero flute for anything that I countersink with a (cordless) drill. They're mostly deburring tools, but I've used them for unceremoniously countersinking a flat head screw as well.
I like a fluted (1 to many, who cares?) countersink for chamfers or actual countersinks made in the mill - particularly if you're trying for a very light chamfer. I've never found a difference one way or t'other in the number of flutes.

GsT

 

[wayback machine]

+1 on the zero flute type - I seem to get less chatter with those, no matter what the set up.
YMMV